1. Department of Physics, Duke University, Durham, North Carolina27708, United States
2. Department of Physics and Astronomy, Appalachian State University, Boone, North Carolina28607, United States
3. Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba305-0044, Japan
4. International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba305-0044, Japan